1. Field of the Invention
The invention relates to wireless communications and more particularly to data coding and decoding in wireless communications.
2. Background
System resources are often wasted when a cellular wireless communication device can communicate with multiple (more than one) transmission sources. If multiple sources transmit the same information, the sources may increase the interference in the system for other users. Additionally, more network resources may be consumed, such as, for example, by increasing back haul traffic. Back haul traffic is traffic on the network side of an air interface, such as a base station. Thus, for example, in an IS-95 system, an example of back haul is data traffic between a base station and a base station controller.
Resources are also wasted, for example, in soft hand-off (SHO) in cellular wireless communication systems such as, for example, code division multiple access (CDMA). In SHO, a mobile wireless communication device is being transferred from one base station to another base station, based on received signal levels from the two base stations. The mobile station receives data from both the base stations for short duration before a complete hand-off to the next base station is completed. See generally, TIA-2000.5-D “Upper Layer (Layer 3) Signaling Standard for cdma2000® Spread Spectrum Systems”, March 2004, Section 2.6.6, pages 2-471 to 2-619. Typically in SHO, multiple base stations transmit the same information at the same time so that the receiver can combine the information at its front-end. But SHO creates waste through redundancy.
One solution to the problem is cell selection in packet data systems such as IS-856. In cell selection, the cellular wireless communication device determines which of the available transmission sources should send packets. The chosen transmission source sends the next packet, and the other available transmission sources do not send packets.
A first problem with the cell selection solution is that the transmission sources may not know which packets the cellular wireless communication device has received from other transmission sources, and therefore, the transmission sources may send multiple copies of the same packets, wasting system resources. A solution for the first problem with the cell selection solution is for the cellular wireless communication device to give a next packet indicator in a signaling or other overhead channel, to inform the transmission sources which packet to send, as described in U.S. Pat. Appl. Pub. No. 2002/0145991 A1, published on Oct. 10, 2002, which is hereby incorporated by reference in its entirety.
A second problem with the cell selection solution is increased overhead signaling. Increased overhead signaling occurs regardless of whether the cellular wireless communication device gives a next packet indicator. Increased overhead signaling occurs because the cellular wireless communication device must tell the transmission sources (1) which transmission source should transmit next and, optionally, (2) which packet should be sent next. Transmitting and tracking this information causes overhead and possibly delay in the system.
Cell-Selection also takes away the advantage of combining information from multiple base stations, especially, at the hand-off regions where signal strength from all the base stations could be weak.